The present invention relates to machines for applying tape to boxes.
Examples of devices for applying adhesive coated tape to boxes and like objects are described in the Collet et al. U.S. Pat. No. 3,915,786, the Patterson U.S. Pat. No. 3,954,550, and the Deering, Jr. U.S. Pat. 4,238,269. In addition, Minnesota Mining and Manufacturing Company of Saint Paul, Minn., manufactures and markets a line of tape applying machines sold under the trademarks 3M-MATIC 22A ADJUSTABLE CASE SEALER, 3M-MATIC 77A ADJUSTABLE CASE SEALER, and 3M-MATIC 77R RANDOM CASE SEALER.
Such machines have removable taping heads which from time to time need to be removed from the machine for maintenance. In the case of the tape applying machines marketed by Minnesota Mining and Manufacturing Company, the upper taping heads are secured within the machine by four screws. Although this permits the removal of the taping heads relatively easily, there is a need for removing the taping heads in a more convenient and efficient manner.
In such machines, there is typically an upper taping head and a lower taping head so that both the upper and lower flaps of a box are sealed simultaneously, as the box travels through the machine. In operating such machines on a continual basis, an operator must monitor the amount of tape on the supply roll so that the taping machine does not run out of tape. In the case of the upper taping head, this is not a problem since the supply roll of tape is easily viewable. However, with respect to the lower taping head, the roll of tape is typically beneath the carriage of the taping machine, and it is often times difficult to keep track of how much tape is left on the supply roll.
Such machines also include conveyor sections that are detachably attachable to the carriage of the machine. The conveyors have freely rotatable rollers on which boxes travel into the tape applying machine, and on to which boxes travel out of the tape applying machine. It is important that such conveyors be level since the rollers are freely rotatable, so that the boxes do not drop off the conveyors when left unattended. Short conveyor sections do not have their own legs and are typically hung from the carriage, the extent to which such conveyors are level depends on the leveling of the machine and the point of attachment to the conveyor. In the normal course of operating such machines, operators and other personnel may lean on the conveyor sections or heavy boxes may be placed on the conveyor sections, weakening the connection to the machine, and affecting the degree to which the conveyors are leveled.
Another problem with prior art conveyors involves the freezing of bearings on which the rollers rotate. Such rollers revolve about shafts that are fixedly attached to side frame members at both of the shaft's ends. However, the bearings on which such shafts rotate occasionally freeze due to the invasion of dust, dirt, and foreign objects into the bearings. As boxes travel over a frozen conveyor roller, the force applied by the traveling box is transmitted as torque on the shaft. In the prior art, such shafts are attached to the side frames of the conveyor through the use of a hex-configured end portion that fits into a hex hole in the side frame. Eventually, the torque that is transmitted by boxes rolling over a frozen roller will twist the shaft in the hex hole, stripping the hex hole and thereby causing a more expensive repair. Since such frozen shafts are not easily detectable, the turning of the shaft within the now worn out hex hole can continue for an extensive period of time and cause considerable damage to the conveyor frame.
Another problem exists in tape applying machines which automatically center boxes as they travel through the machine, and which adjust the height of the upper taping head to accommodate boxes of various heights. The structure that holds the upper taping head is adjustable through a pair of pneumatic cylinders that are activated by a switch that is engaged by a box traveling through the machine. This system works very well. However, with new regulations promulgated under the Occupational Safety and Health Act, all industrial machines cannot have any stored energy within the machine. In the case of a pneumatically operated machine, the pressurized air must be relieved when the machine is shut off. This results in a problem for performing maintenance on the bridge structure of automatically adjustable tape applying machines, since the bridge structure will be in the down position when the machine is shut off. There are instances in which the bridge structure is needed in the up position to perform maintenance.
To tape the top flaps of boxes, a compression roller on either side of the box has been positioned in prior art tape applying machines. The compression roller engages a top portion of the box and attempts to ensure that the edge portions of the flaps are in abutting relationship. However, parallel taping of the edge portions of the top flaps of the box has not always been successful using such compression rollers.